Abstract

A dual sensor probe array is designed and constructed for internal magnetic field measurement at Versatile Experiment Spherical Torus (VEST) at the Seoul National University. Simultaneous use of Hall sensors and chip inductors allows cross-calibration among the measurements and compensation for each other's weaknesses while their small sizes are expected to cause only mild plasma perturbations. Calibration of the dual sensor probe array, using a Helmholtz coil, shows good sensitivity for the magnetic field measurement of the VEST. Prior to Ohmic start-up, the magnetic field structure inside the vacuum chamber is measured by using the calibrated probe array. The dual sensor probe array is expected to be useful in analyzing the temporal magnetic field structure change during the magnetic reconnection and in reconstruction of the current profile during the discharge of the VEST device.

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea Government (MEST) (Grant No. 2012-0000587). Authors would like to thank technicians Gilhwan Choi and Jisun Jung for their devotion in the construction and installation of the dual sensor probe array at VEST. We also send our gratitude to the other VEST staffs Hyun Yeong Lee, Jeongwon Lee, and Young-Gi Kim for sharing their opinions in various parts of this work.